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1.
The stability of crack which is present in an adhesive layer is investigated. The adhesive layer bonds an elastic plate to a rigid base. A Wieghardt base is assumed as the model for the adhesive layer. The crack is loaded by internal pressure. An energy criterion and a critical load intensity criterion are used. Explicit results are given for a relatively rigid plate and for a relatively flexible plate and a comparison of the two criteria is discussed. 相似文献
2.
A number of numerical codes have been written for the problem of finding the circle of smallest radius in the Euclidean plane that encloses a finite set P of points, but these do not give much insight into the geometry of this circle. We investigate geometric properties of the minimal circle that may be useful in the theoretical analysis of applications. We show that a circle C enclosing P is minimal if and only if it is rigid in the sense that it cannot be translated while still enclosing P. We show that the center of the minimal circle is in the convex hull of P. We use this rigidity result and an analysis of the case of three points to find sharp estimates on the diameter of the minimal circle in terms of the diameter of P. 相似文献
3.
纤维增强塑料(FRP)与混凝土的粘结性能是混凝土结构外贴FRP板材这一加固技术的重要研究课题。本文通过对混凝土表面粘贴FRP板的单剪搭接接头进行三维有限元模拟,得出了胶和混凝土中在加载端和自由端附近的各应力分量的分布曲线以及FRP板中沿板长度方向的应力分布曲线,从而分析板宽对FRP-混凝土粘结界面应力分布的具体影响,以期为进一步的相关研究提供参考。研究结果表明:(1)沿着板宽度方向应力存在着严重的不均匀性;(2)随着板宽的增加,使得应力沿着板宽的方向渐趋于均匀,因而有利于应力的传递;(3)当宽度比较大时,易发生自由端混凝土的拉剪破坏。 相似文献
4.
Optimal piezo-actuator sizes and locations for a frame structure under bending load uncertainty are determined with the objective of minimizing the deflection under worst case of loading. The bending moments generated by the piezo-actuators are used for deflection control, i.e., to minimize the maximum deflection. The frame is subjected to a tip load which lies in an uncertainty domain with regard to its magnitude and direction. The specific uncertain loading studied in the present paper involves a load of given magnitude but of unknown direction, which should be determined to produce the highest deflection. The worst case of loading depends on the size and location of the actuators leading to a nested problem of optimization (design) and anti-optimization (uncertainty problem). Results are given for deterministic and uncertain loading conditions. 相似文献
5.
嘉绍通道长山河特大桥位于嘉兴海宁市扬汇桥村,桥长1061 m。桩径1.8 m,桩长92 m,属于超长钻孔灌注桩。为了测定桩身的抗压极限承载力,对试桩采用自平衡测试法进行了静载试验。基于实测数据,对桩总承载力、桩侧摩阻力、桩端承载力、桩身变形、位移以及承载性能进行了分析,并将桩端承载力实测值和公路桥涵地基基础规范计算值进行了对比。研究表明桩侧摩阻力提供了大部分的承载力;施工工艺对超长桩承载力有很大影响;控制沉降同时也要控制桩身压缩变形。成功地确定了超长钻孔灌注桩的单桩极限承载力以及承载力性能,位移特征,可为类似工程参考。 相似文献
6.
Jacob Feld 《Journal of The Franklin Institute》1930,209(1):83-108
For long span cables, either with or without concentrated load, the usual methods of design are found to be inaccurate because they omit the elastic stretch of the cable and they assume an inaccurate shape of the resulting curve. Equations are derived to cover all possible cases, loaded and unloaded cable, based upon assumptions of elastic flexible cables with fixed supports. Equations are also derived showing the variation in several quantities with changes in temperature and movement of supports. Conditions of possible loads and elastic properties of cables are discussed. A bibliography covering major references to the subject is included. 相似文献
7.
David S. Ross 《Journal of The Franklin Institute》2010,347(7):1281-1308
If a circle in the plane is to roll along a track so that a given point on the circle traces out another circle, what must the shape of the track be? In this paper we give a full answer to this question. This question arises in the design of internal combustion engines and other machines. It is a sort of inverse problem to the classical problem of the trajectories of points on circles rolling inside other circles; the problem whose solution is hypocycloids and hypotrochoids. We derive a system of nonlinear differential equations for the coordinates of the track regarded as a parametric curve. We express the solution of this differential equation in terms of an elliptic integral. We establish the uniqueness of this solution for a given choice of the relevant parameters, the radius of the circle to be traced out and the location on the rolling circle of the tracing point. We show that if we allow the rolling circle to intersect the track, there is at least one track for any circle. We find all possible tracks, and we derive formulas to determine, for a given radius of the circle to be traced out, how many different tracks produce circles of that radius; there is always a finite number, and the number increases roughly linearly with the radius. We characterize those tracks that are mathematical solutions but are not practical physical solutions; tracks that the rolling circle intersects in such a way that it would get stuck. 相似文献
8.
试图通过技术进步的偏向进行分析,即实际工资的变化趋势依赖于技术进步的偏向:技术进步偏向利用资本、节约劳动时,实际工资呈下降趋势;技术进步偏向利用劳动、节约资本时,实际工资呈上升趋势。我国经济发展的实证研究也为上述研究提供了支持。 相似文献
9.
We present the mathematical model and an artificial neural network method for calculating the buckling load of a beam column with different end conditions. A trial solution of the beam column equation is written as a sum of two parts, in which first part satisfies the boundary conditions and the second part represents the feed forward neural network containing adjustable parameters, weights and biases. We prepared the Error function by using the beam column equation and its boundary conditions, which is used in the back propagation method with deflection term to update the network parameters. It is found that the artificial neural network method is capable for calculating deflection of a beam column as a part of the training process. To ascertain the soundness, efficiency and accuracy of the proposed method the results are compared to the Euler critical load. 相似文献
10.
高铁驱动下大尺度区域都市圈旅游空间结构优化——以京沪高铁为例 总被引：5，自引：0，他引：5
高铁"时空压缩"效应使都市圈旅游辐射范围进一步扩大。以都市圈为基本空间结构单元,分析高铁驱动下大尺度区域旅游空间结构优化具有重要意义。本文运用"核心-边缘"和"板块旅游"空间结构理论,结合京沪高铁线6个都市圈基本特征以及高铁旅游流空间网络结构和空间效应特征,通过节点优化,线状连接和面状拓展等空间优化路径,确定大尺度区域重点旅游发展点、旅游发展轴和旅游地系统,构建不同等级的旅游板块。通过一级核心旅游点和一级旅游地系统的核心扩散作用,将二级旅游板块和三级旅游板块由一、二、三级扩展轴融入一级旅游板块中,最终建构京沪高铁旅游带。高铁"时空压缩"效应使高铁旅游带的各都市圈空间联系增强,应加强都市圈区域旅游合作,进一步发挥高铁扩散效应和叠加效应,促使"旅游高地"不是对"旅游洼地"产生虹吸现象,而是更多发挥"旅游高地"的"溢出效应",带动"旅游洼地"发展,进而实现高铁区域旅游一体化发展的目标。 相似文献
11.
In this study, the homotopy analysis method (HAM) is used to obtain an approximate analytical solution for geometrically non-linear vibrations of thin laminated composite plates resting on non-linear elastic foundations. Geometric non-linearity is considered using von Karman’s strain-displacement relations. Then, the effects of the initial deflection, ply properties, aspect ratio of the plate and foundation parameters on the non-linear free vibration is studied. Comparison between the obtained results and those available in the literature demonstrates the potential of HAM for the analysis of such vibration problems, whose governing differential equations include the quadratic and cubic non-linear terms. This study shows that only a first-order approximation of the HAM leads to highly accurate solutions for this type of non-linear problems. 相似文献
12.
In this study, a viscometer, which can measure the viscosity of low-volume liquids (25 μl) within 30 s, was developed on a centrifugal platform. The centrifugal viscometer consists of a disk platform and a motor. Under disk rotation, centrifugal, Coriolis, and viscosity-induced drag forces result in deflection of liquid flow. The viscosity of the liquid sample is determined by the deflection angle of the liquid, which can be examined through image analysis or visual inspection. The viscosities of a series of Newtonian model fluids were tested by the centrifugal viscometer and the results showed good agreement with the ones tested by a conventional rotational viscometer. Since the centrifugal viscometer only requires a motor to function, the microfluidic disk can be produced in large quantities at a low cost through injection molding, and the deflection angle can be detected through visual inspection, it provides an inexpensive, easy to operate, and portable approach to measure low-volume liquid viscosity. 相似文献
13.
Xinwei Wang Chao Han Yuanjin Yu Zhaohua Yang 《Journal of The Franklin Institute》2018,355(7):3274-3287
A modified adaptive backstepping tracking method is proposed to improve the tracking performance of the magnetic bearing system with nonlinear magnetic toque. For a magnetically suspended momentum wheel, two dimensional gyroscopic torque can be produced when the rotor shaft is actively deflected by the active magnetic bearing. High precision rapid tracking control of shaft deflection is desiderated to provide high precision and wide bandwidth outputting torque. The nonlinearity of magnetic bearing is analyzed initially, and the stiffness coefficients of magnetic bearing can be treated as bounded continuous functions with respect to deflection angles. A fuzzy function based adaptive law is proposed to estimate the stiffness coefficients. Combining with a modified backstepping method, the proposed control strategy can deal with the nonlinearity efficiently when the shaft deflects rapidly, and its stability is proved by Lyapunov stability theory. To validate the effectiveness of this method, numerous simulations are performed and the results indicate that this method improves the tracking precision when tracking high frequency reference deflection angles. 相似文献
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15.
In connection with an investigation that involved the measurement of optical path-difference and thence birefringence it became necessary to have much higher accuracy than is ordinarily attained. After a careful study of the various methods available it appeared that the one which best meets the requirements of precision and simplicity is a method first elaborated by Friedel (1893), and based on an interesting property possessed by a fixed combination of (1) a polarizer, (2) the birefracting material, and (3) a quarter-wave plate, each placed in a definite orientation to the others. When plane parallel monochromatic light passes through the elements of this fixed combination in the order shown above, the emergent light is plane polarized and the azimuth is related in a simple manner to the path-difference of the specimen. Since this azimuth can be measured by means of an analyzer and graduated circle, the determination of path-difference thus reduces itself to the measurement of an angular displacement, which can be done easily and with high precision.The method was first made applicable to a petrographic microscope for the purpose of determining the path-difference at a given spot in small specimens. Later, there was constructed a separate polarimeter in which large specimens could be conveniently measured. This instrument has given all that was expected of it in facility and rapidity of taking readings, and for any path-difference has a sensitivity about one hundred times greater than that of the devices in common use.A resumé of the general relations for elliptically polarized light as applied to the present method is given, and the magnitude of the errors that may arise is discussed in detail. 相似文献
16.
该研究以江苏理工学院2018级非英语专业选修学术英语(理工)课程的学生为研究对象,设计英语阅读态度调查量表对参与研究的学生进行问卷调查,以了解12周的“文学圈”阅读模式教学后学生英语阅读态度的变化。研究数据显示,实验组学生的英语阅读态度总体上呈现改善趋势;阅读态度的三个维度中,情感维度和行为倾向维度的大部分指标皆有不同程度的增加。这在一定程度说明“文学圈”阅读教学模式对非英语专业大学生的阅读态度有积极的影响。 相似文献
17.
W.E. Danforth 《Journal of The Franklin Institute》1935,219(3):377-378
The method of analyzing the results of cosmic ray deflection experiments, developed in a previous paper, is here extended to the case where the region of uniform deflecting field is of the same width as that of the counters. In this form it is applicable to the electrostatic deflection experiment of Lenz, and to the electrostatic and magnetic experiments of W. F. G. Swann and the writer. The magnetic experiments of Curtiss and of Mott-Smith are reexamined in the light of the energy distribution recently published by Anderson and Nedderineyer. The latter's result is found to be not inconsistent with the assumption that the induction B gives the correct force; the result of the former requires the addition of low energy rays to the distribution. 相似文献
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Kihoon Jang Yo Tanaka Jun Wakabayashi Reina Ishii Kae Sato Kazuma Mawatari Mats Nilsson Takehiko Kitamori 《Biomicrofluidics》2012,6(4)
Demand for analysis of rare cells such as circulating tumor cells in blood at the single molecule level has recently grown. For this purpose, several cell separation methods based on antibody-coated micropillars have been developed (e.g., Nagrath et al., Nature 450, 1235–1239 (2007)). However, it is difficult to ensure capture of targeted cells by these methods because capture depends on the probability of cell-micropillar collisions. We developed a new structure that actively exploits cellular flexibility for more efficient capture of a small number of cells in a target area. The depth of the sandwiching channel was slightly smaller than the diameter of the cells to ensure contact with the channel wall. For cell selection, we used anti-epithelial cell adhesion molecule antibodies, which specifically bind epithelial cells. First, we demonstrated cell capture with human promyelocytic leukemia (HL-60) cells, which are relatively homogeneous in size; in situ single molecule analysis was verified by our rolling circle amplification (RCA) method. Then, we used breast cancer cells (SK-BR-3) in blood, and demonstrated selective capture and cancer marker (HER2) detection by RCA. Cell capture by antibody-coated microchannels was greater than with negative control cells (RPMI-1788 lymphocytes) and non-coated microchannels. This system can be used to analyze small numbers of target cells in large quantities of mixed samples. 相似文献
20.
科学性是现代立法的基本属性之一。经考察发达国家立法实践发现,为实现立法的科学性,科技界建制化参与立法已成趋势。而我国科技界建制化参与立法的制度保障明显不足,并进而导致立法过程的科技论证与支撑不足、立法对科技迅速发展的挑战应对不足等问题。我国应借鉴发达国家的立法经验,立足国情,为科技界建制化参与立法提供制度保障,建立科技界与立法机关的常态化交流平台。 相似文献